G'day Ion. Ion Gaztañaga <igaztanaga <at> gmail.com> writes:
I hope you can find to do a review, since it seems you have experience with memory mappings.
I hope so too. :-)
If I understand this correctly, you want a class that can map more than a fragment of a file holding a single file descriptor, is that right?
Well... I want a way to do that, whether it's a single class or not. When I first thought about it, the approach that I considered was to use two classes. mmaped_file represents a file which has zero or more mmaped regions, and mmaped_region which represents a single region. Off the top of my head, something like this might be appropriate: class mmapped_file : private boost::noncopyable { public: /* A slightly richer set of access modes. If the operating system does not support some mode, the library should pick a mode that at least allows the required mode. (e.g. if the OS doesn't support write-only mode, read-write mode is an appropriate substitute since it allows writing. */ typedef enum { none_mode = 0x00, ro_mode = 0x01, wo_mode = 0x02, rw_mode = 0x03, access_mode_mask = 0xff } accessmode; /* Open a file, RAII style. Throws an exception on failure. */ mmapped_file(const char* filename, accessmode mode); /* Closes the file. Does not throw. */ ~mmapped_file(); /* XXX Support for iterating through the mapped regions? */ }; class mmaped_region : private boost::noncopyable { public: /* Map a region from an mmaped_file. Throws an exception on failure. */ mmaped_region(shared_ptr<mmaped_file>& file, fileoff_t offset, size_t size, mmaped_file::accessmode mode); /* Unmap the region. Does not throw. */ ~mmapped_region(); /* Get the size of the mapped region. Does not throw. */ std::size_t get_size() const; /* Get a pointer to the base of the mapped region. Does not throw. */ void* get_base() const; /* Get the file offset of the beginning of the mapped region. Does not throw. */ fileoff_t get_file_offset() const; /* Flush an area of the mapped region. Does not throw. */ bool flush(size_t mapping_offset = 0, size_t numbytes = 0); }; mmaped_region holds a shared_ptr to an mmaped_file, so that when the last mapped region is destroyed, the file is closed (assuming someone else isn't holding onto if, of course). Cheers, Andrew Bromage